Establishment of tagasaste (Chamaecytisus palmensis (Christ) Bisby et K. Nicholls)

Abstract

Tagasaste, a shrub legume, has the potential to provide stock feed where the growth of conventional legumes is limited. This research project was undertaken to determine the appropriate management techniques for establishing tagasaste (Chamaecytisus palmensis). Field trials were conducted at Lincoln, Canterbury, during the 1984-1985 spring and summer. Experiments were also carried out in the glasshouse and laboratory.

Untreated tagasaste seeds of two seedlines gave less than 5% germination. Mechanical scarification gave over 90% and is the recommended treatment, although hand chipping and concentrated sulphuric acid treatments gave similar results in these seedlines. The formerly recommended hot water treatment gave germination varying between 20% and 60%, and resulted in a high proportion of abnormal seedlings. The most common abnormality was caused by failure of the cotyledons to free themselves from the testa. Treating the seeds with alternating water temperatures only marginally improved the results. Tagasaste seeds germinated best at temperatures of 16°C to 20°C (75%) and poorly below 5°C and above 30°C (<10%). Seed germination was slow at 9°C and 24°C, but the final percentages were satisfactory (60% and 70% respectively).

Tagasaste seeds broadcast on short, dead vegetation cover gave 11% established seedlings, but seeds broadcast on bare, cultivated ground did not establish. Establishment of seeds sown at 1cm depth was 65% for both cultivated and herbicidal treatments, but at 3cm and 5cm depth cultivation gave significantly fewer established plants (57% and 73% at 3cm, and 47% and 61% at 5cm).

Tagasaste was found to be extremely vulnerable to weed competition, and % surviving seedlings in the weedy plots was only half that of hand-weeded plots. "Surviving seedlings which suffered weed competition produced less than one tenth of weeded plant top dry weight.

Tagasaste yielded 75% more than red clover with no P or S applied, when grown on a Takahe-Cashmere hill soil complex in a pot experiment (Olsen P 4, pH 5.6), Red clover responded strongly to S, when P was applied, but tagasaste did not. When 80 mg S/pot was applied, the yield of red clover at high P (160 mg P/pot) was 53% higher than that of tagasaste. When S was not applied, both species produced similar yields at high P.

In conclusion, tagasaste seed is probably better treated with mechanical scarification than with hot water or acid. Further establishment trials should be carried out on hill country to study the result of broadcasting tagasaste on short, dead vegetation cover. Agronomic practices must aim to obtain maximum seedling growth, and the existing vegetation must be treated with a herbicide, in view of the vulnerability of tagasaste seedling to weed competition. Sowing from early to mid spring may give the best establishment results, but this has to be tested under field conditions. Field trials are also necessary to confirm the performance of tagasaste on P deficient soils.